How to Wire a Switch With White, Black and Ground Wires

A 120-volt switch has hot and ground terminals, but none for neutral.

The hot wire in a 120-volt residential AC circuit usually is coated with black insulation, while the return, or neutral, wire is white. A single-pole, single-throw switch — such as a light switch — works by interrupting the hot wire, so it has two brass terminals for the hot connections and no silver terminals for neutral. Hooking up a switch is the essence of simplicity. You connect the black wires in the electrical box to the switch terminals, and the white wires to each other. The switch also has a green terminal for the ground wires, which usually are bare.

1

Turn off the power to the circuit before you begin wiring the switch. Find the breaker in the main panel that controls the circuit and turn it off.

2

Feed the circuit cable through the back of the switch box and pull out about 6 inches of slack. Run another cable of the same gauge to the fixture you want the switch to control. Feed the end of that wire through the back of the box and pull out the same amount of slack.

3

Cut the plastic covering off of the ends of the cables, using a utility knife. Pull the wires apart. Trim 1/2 inch of insulation from the ends of the black and white cables.

4

Connect the black wires to the switch terminals. The switch simply interrupts the current so it doesn't matter to which terminal you connect either wire. If the switch has self-clapming holes behind the terminals, insert the end of each wire into a hole. If not, bend each wire clockwise, hook it around a screw and tighten the screw, using a screwdriver.

5

Splice the white wires together by twisting the ends together clockwise, using pliers. Screw on a wire cap to hold them together and insulate the ends.

6

Crimp the bare ground wires together with a crimp connector. Wrap the end of the one of the ground wires around the green ground screw on the switch and tighten the screw, using a screwdriver.

Things You Will Need

Utility knife

Screwdriver

Wire cap

Crimp connector

Crimping tool

Tip

It's usually easiest to run cables through the attic or basement and pass them vertically to the switch.

If you're wiring a new switch in an existing wall, you can save time by installing a remodeling box. Instead of nailing it to a stud, you can attach it directly to the surface of the drywall.

Warning

The cable you use to connect the fixture to the switch must be identical to the cable that feeds the circuit. The National Electrical Code forbids changing wire gauge in the middle of a circuit because it can start a fire.